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Table 7. Electrocoagulation techniques and recent research trends.

Table 7 Electrocoagulation techniques and recent research trends.

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Table 1. Advantages and disadvantages of electrochemical processes mainly used to remove nutti- ent matter. EC processes are promising alternatives to traditional physical and chemical wastewater treatment methods, addressing several key limitations of these conventional approaches. Notable advantages include high energy efficiency, cost-effectiveness, ease of automation, and a significant reduction in chemical consumption and sludge production [11]. Moreover, EC treatment effectively reduces chemical oxygen demand (COD) and color in wastewater, enabling compliance with stringent discharge standards while also potentially yielding valuable by-products, such as metal coatings, depending on the wastewater composition [33]. A major benefit is the high selectivity for removing specific nutrients achieved by adjusting electrode materials and reaction conditions. By minimiz- ing the use of chemicals, relying primarily on electricity, EC methods avoid secondary pollution and are compatible with renewable energy sources, such as solar photovoltaic (PV) electricity generation, a well-established, sustainable, and environmentally friendly energy source [34]. Since PV technology now produces the lowest-cost electricity in his- tory [35], it can be used to accelerate the point at which EC wastewater treatment is eco- nomically viable. This approach is particularly promising, as wastewater treatment with EC methods can act as a dispatchable load to help manage the intermittent availability 36] of renewable energy resources.
Table 1. Advantages and disadvantages of electrochemical processes mainly used to remove nutti- ent matter. EC processes are promising alternatives to traditional physical and chemical wastewater treatment methods, addressing several key limitations of these conventional approaches. Notable advantages include high energy efficiency, cost-effectiveness, ease of automation, and a significant reduction in chemical consumption and sludge production [11]. Moreover, EC treatment effectively reduces chemical oxygen demand (COD) and color in wastewater, enabling compliance with stringent discharge standards while also potentially yielding valuable by-products, such as metal coatings, depending on the wastewater composition [33]. A major benefit is the high selectivity for removing specific nutrients achieved by adjusting electrode materials and reaction conditions. By minimiz- ing the use of chemicals, relying primarily on electricity, EC methods avoid secondary pollution and are compatible with renewable energy sources, such as solar photovoltaic (PV) electricity generation, a well-established, sustainable, and environmentally friendly energy source [34]. Since PV technology now produces the lowest-cost electricity in his- tory [35], it can be used to accelerate the point at which EC wastewater treatment is eco- nomically viable. This approach is particularly promising, as wastewater treatment with EC methods can act as a dispatchable load to help manage the intermittent availability 36] of renewable energy resources.
Figure 1. Trend in the number of documents in the Scopus database from 2014 to 2023. ‘electrochemistry’, ‘water’, ‘electrode’, ‘treatment’, and ‘wastewater’ in the title, abstract, or keywords. The search covered the period from 2014 to 2023, and the results were fur- ther classified into experimental studies and review articles. The number of experimental articles related to ‘water’ and ‘wastewater’ rose from 17 to 83 (a 68.8% increase), while review articles increased from 3 to 31 (a 101.4% increase). This trend highlights the grow- ing interest in electrochemical methods for wastewater treatment, driven by the need for more sustainable and efficient solutions. The classification into experimental and review papers was conducted by reviewing the abstracts and determining whether the studies reported new experimental data or provided a summary of the existing literature. The numbers in Figure 1 represent the annual publication count, with each bar reflecting the number of publications each year. Similarly, when searching the Web of Science database using the same keywords, the trend from 2014 to 2023 also showed a significant increase in experimental studies. From 2014 to 2023, the number of experimental articles related to ‘water’ and ‘wastewater’ rose from 47 in 2014 to 102 in 2023, representing an increase of approximately 117.02%. This result further underscores the growing momentum in re- search focused on electrochemical wastewater treatment technologies.
Figure 1. Trend in the number of documents in the Scopus database from 2014 to 2023. ‘electrochemistry’, ‘water’, ‘electrode’, ‘treatment’, and ‘wastewater’ in the title, abstract, or keywords. The search covered the period from 2014 to 2023, and the results were fur- ther classified into experimental studies and review articles. The number of experimental articles related to ‘water’ and ‘wastewater’ rose from 17 to 83 (a 68.8% increase), while review articles increased from 3 to 31 (a 101.4% increase). This trend highlights the grow- ing interest in electrochemical methods for wastewater treatment, driven by the need for more sustainable and efficient solutions. The classification into experimental and review papers was conducted by reviewing the abstracts and determining whether the studies reported new experimental data or provided a summary of the existing literature. The numbers in Figure 1 represent the annual publication count, with each bar reflecting the number of publications each year. Similarly, when searching the Web of Science database using the same keywords, the trend from 2014 to 2023 also showed a significant increase in experimental studies. From 2014 to 2023, the number of experimental articles related to ‘water’ and ‘wastewater’ rose from 47 in 2014 to 102 in 2023, representing an increase of approximately 117.02%. This result further underscores the growing momentum in re- search focused on electrochemical wastewater treatment technologies.
In conclusion, electrodes such as Pt, DSA, BDD, graphite, and MOFs each possess unique advantages and disadvantages, allowing them to be selectively used in EC wastewater treatment under specific conditions. By leveraging the characteristics of these materials, the efficiency and application range of EC wastewater treatment can be signifi- cantly improved. Understanding and applying the optimal conditions for each electrode material will enable the implementation of more effective and sustainable wastewater treatment solutions. The selection of electrode materials is crucial for optimizing the per- formance of EC wastewater treatment systems. Although an ideal anode has not been clearly established, significant progress has been made. Continued research and develop- ment are necessary to overcome existing limitations and enhance the applicability of this technology. Focus areas should include improving cost efficiency, durability, and catalytic efficiency, which are essential to meet the demand for sustainable wastewater treatment solutions. Table 3. Cathode materials in electrochemical processes.
In conclusion, electrodes such as Pt, DSA, BDD, graphite, and MOFs each possess unique advantages and disadvantages, allowing them to be selectively used in EC wastewater treatment under specific conditions. By leveraging the characteristics of these materials, the efficiency and application range of EC wastewater treatment can be signifi- cantly improved. Understanding and applying the optimal conditions for each electrode material will enable the implementation of more effective and sustainable wastewater treatment solutions. The selection of electrode materials is crucial for optimizing the per- formance of EC wastewater treatment systems. Although an ideal anode has not been clearly established, significant progress has been made. Continued research and develop- ment are necessary to overcome existing limitations and enhance the applicability of this technology. Focus areas should include improving cost efficiency, durability, and catalytic efficiency, which are essential to meet the demand for sustainable wastewater treatment solutions. Table 3. Cathode materials in electrochemical processes.
Table 4. Selected examples of the electrochemical treatment of nutrient pollutants.
Table 4. Selected examples of the electrochemical treatment of nutrient pollutants.
3.3. Electrochemical Ammonia Oxidation Electrochemical ammonia oxidation (EAO) is an innovative technique for the re- moval of ammonia from wastewater. This process operates in an electrochemical (EC) cell where ammonium (NHs*) undergoes oxidation at the anode. The appeal of EAO lies in its high efficiency, scalability, and ability to function under ambient conditions without chemical additives. This section explores the mechanisms underlying EAO while also highlighting recent advancements and research developments in this field [92]. The fun- damental principle of EAO involves the direct oxidation of ammonium to nitrogen gas (Nz) or other nitrogen compounds at the anode. The overall reaction is typically repre- sented by Equation 12.
3.3. Electrochemical Ammonia Oxidation Electrochemical ammonia oxidation (EAO) is an innovative technique for the re- moval of ammonia from wastewater. This process operates in an electrochemical (EC) cell where ammonium (NHs*) undergoes oxidation at the anode. The appeal of EAO lies in its high efficiency, scalability, and ability to function under ambient conditions without chemical additives. This section explores the mechanisms underlying EAO while also highlighting recent advancements and research developments in this field [92]. The fun- damental principle of EAO involves the direct oxidation of ammonium to nitrogen gas (Nz) or other nitrogen compounds at the anode. The overall reaction is typically repre- sented by Equation 12.
Table 5. EAO techniques and recent research trends. Despite these advancements, challenges remain in the long-term stability and fouling of electrodes. The development of fouling-resistant materials and effective cleaning pro- tocols is essential for practical applications. Enhancing the energy efficiency of EAO is also critical for its economic viability. Thus, research is focused on optimizing electrode mate- rials and operational parameters to reduce energy consumption. Additionally, integrating EAO with other treatment technologies, such as biological treatment or advanced oxida- tion processes, could provide synergistic benefits, improving overall treatment efficiency and cost-effectiveness [103]. +r — . tee . ee . 4 1 a . 4
Table 5. EAO techniques and recent research trends. Despite these advancements, challenges remain in the long-term stability and fouling of electrodes. The development of fouling-resistant materials and effective cleaning pro- tocols is essential for practical applications. Enhancing the energy efficiency of EAO is also critical for its economic viability. Thus, research is focused on optimizing electrode mate- rials and operational parameters to reduce energy consumption. Additionally, integrating EAO with other treatment technologies, such as biological treatment or advanced oxida- tion processes, could provide synergistic benefits, improving overall treatment efficiency and cost-effectiveness [103]. +r — . tee . ee . 4 1 a . 4
Table 6. Comparative analysis of electrochemical methods vs. traditional nutrient removal technol ogies [119-121]. As there are still few studies on the large-scale application of EC processes for nutri- ent removal, this review presents performance data collected from various pilot projects and studies to evaluate the feasibility of EC nutrient removal technologies (Table 7) [122]. The results of pilot tests demonstrate that EC methods show high efficiency and maintain stable performance under various environmental conditions.
Table 6. Comparative analysis of electrochemical methods vs. traditional nutrient removal technol ogies [119-121]. As there are still few studies on the large-scale application of EC processes for nutri- ent removal, this review presents performance data collected from various pilot projects and studies to evaluate the feasibility of EC nutrient removal technologies (Table 7) [122]. The results of pilot tests demonstrate that EC methods show high efficiency and maintain stable performance under various environmental conditions.
These studies illustrate the diverse applications and effectiveness of various electrode materials in the EC treatment of wastewater, demonstrating the potential for industrial use as well as the challenges to scale-up. These case studies prove the potential for com- mercializing EC wastewater treatment and provide foundational data for the develop- ment of large-scale systems. Despite promising results obtained from laboratory-scale tests, the industrial application of anodic oxidation for organic pollutant treatment re- mains limited. Example process flow diagrams (PFDs) illustrate how EC methods could be incorporated to achieve multiple treatment objectives, including pollutant removal, nu- trient removal, and water reuse. Meng et al. investigated electrochemical oxidation for removing COD and ammonia nitrogen from high salinity tungsten smelting wastewater 132]. They presented results for the removal of COD and ammonia nitrogen (NH3-N) from high salinity tungsten smelting wastewater (TSW) using one-step EO technology. The research progressed from bench-scale tests through pilot-scale tests, and, finally, to industrial-scale tests with the objective of identifying optimal conditions and assessing scalability to industrial applications. Initially, bench-scale tests were conducted to deter- mine the effects of variables such as current density, anode material, and pH. The findings were then validated through pilot-scale tests, which operated under more realistic condi- tions with a treatment capacity of 200-500 L/h. The final stage involved large-scale indus- trial tests with a capacity of 100 m°/h, designed to assess the practical applicability and economic viability of the EO process.
These studies illustrate the diverse applications and effectiveness of various electrode materials in the EC treatment of wastewater, demonstrating the potential for industrial use as well as the challenges to scale-up. These case studies prove the potential for com- mercializing EC wastewater treatment and provide foundational data for the develop- ment of large-scale systems. Despite promising results obtained from laboratory-scale tests, the industrial application of anodic oxidation for organic pollutant treatment re- mains limited. Example process flow diagrams (PFDs) illustrate how EC methods could be incorporated to achieve multiple treatment objectives, including pollutant removal, nu- trient removal, and water reuse. Meng et al. investigated electrochemical oxidation for removing COD and ammonia nitrogen from high salinity tungsten smelting wastewater 132]. They presented results for the removal of COD and ammonia nitrogen (NH3-N) from high salinity tungsten smelting wastewater (TSW) using one-step EO technology. The research progressed from bench-scale tests through pilot-scale tests, and, finally, to industrial-scale tests with the objective of identifying optimal conditions and assessing scalability to industrial applications. Initially, bench-scale tests were conducted to deter- mine the effects of variables such as current density, anode material, and pH. The findings were then validated through pilot-scale tests, which operated under more realistic condi- tions with a treatment capacity of 200-500 L/h. The final stage involved large-scale indus- trial tests with a capacity of 100 m°/h, designed to assess the practical applicability and economic viability of the EO process.
Figure 2. Structural schematic of the electrolytic cells.
Figure 2. Structural schematic of the electrolytic cells.
Related topics:
ElectrochemistryWater and wastewater treatmentElectrochemical EngineeringSustainable Water Resources ManagementEnvironmental SustainabilityWater Resources engineeringWaste water treatmentNutrient Management
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